The 21-year-old spent a loan spell with Wigan earlier in the season and will return to the Championship after securing a switch to Loftus Road.
Manager Harry Redknapp was glad to add another new face to his squad as he prepares for a final push for promotion.
"Will is a young player with fantastic potential," Redknapp told the club's official website.
"He's got a good eye for goal, leads the line well and will provide us with good competition in the final third.
"We're looking forward to welcoming him into the squad."
Keane admits he welcomed the chance to play under Redknapp and hopes for more first-team action with the R's.
"I had a taste for the Championship in a loan spell at Wigan earlier this season, and really enjoyed that," he said.
"I'm looking to get some more games under my belt, and hoping to help the team get back up to the Premier League.
"I joined because of the manager, he's very experienced and been successful throughout his managerial career. QPR are also a big club.
"This is a good challenge for me - and one I'm looking forward to."